The use of genomically targeted therapies has improved treatment response and clinical outcomes for molecularly defined subsets of patients with non-small cell lung cancers. While responses to these therapies can often be dramatic, they are rarely durable, and there is a significant need to improve the duration of response and delay or prevent treatment resistance. Studies from our group and others have characterized the properties of cancer cells which escape initial treatment with a targeted agent. Analyses of these data have revealed transcriptional and epigenetic adaptation as a requirement for the survival of cells that persist in the face of targeted therapy. Working with Core A (Chemistry) and Core B (Structure), we have obtained Preliminary Data suggesting that inhibitors of higher-order cyclin dependent kinases (CDKs), enzymes which perform key roles in transcriptional initiation and elongation, display potent synergy with targeted kinase inhibitors in a diverse array of NSCLC models both in vitro and in vivo. Specifically, we have identified THZ1, a covalent CDK7/12 inhibitor designed by Core A leader Dr. Gray, as a tool compound which synergizes with inhibitors of EGFR (Project 1), MEK (Project 2) as well as ALK, HER2, BRAF, FGFR and PI3K in genetically selected NSCLC models. In this project, we will advance our efforts in targeting transcriptional adaptation to targeted therapies by using genetic tools to define the key CDK/cyclin genes responsible for therapeutic synergy and using this information to design more selective CDK inhibitors and selective degraders with improved specificity and in vivo pharmacology as compared to THZ1. Further, we will use transcriptional and epigenetic analysis to define the mechanisms governing therapeutic synergy among targeted therapies and CDK inhibitors. This project will be amenable to clinical translation given the broad applicability of this approach and ongoing efforts to develop transcriptional CDK inhibitors for clinical use.